Kling 4.0 Flash Keyframe To Video

Endpoint

POST /jobs/createTask

Full URL: https://modelfold.ai/v1/jobs/createTask

Authentication: every request must include the Authorization: Bearer <API_KEY> header.

Output resolution is always 720p. Duration is 3–20 seconds. When a first frame is provided, the output follows that image's aspect ratio; aspect_ratio is only used when no first frame is sent (default 16:9).

Query Task Status

After submitting a task, you can check the task progress and retrieve generation results via the unified query endpoint:

Get Task Details — Learn how to check the task status and obtain the generated results

TIP

In the production environment, it is recommended to use the callBackUrl parameter to receive the automatic notification upon completion of the generation, rather than polling the status endpoint.

Market Overview — View all available models

Request Parameters

Body (application/json)

Parameter	Type	Required	Description
`model`	`string`	Yes	The name of the model used to generate the task. This field is required. - This endpoint requires the `kling-4.0/flash-keyframe-to-video` model Default：`"kling-4.0/flash-keyframe-to-video"`。 Allowed values：`kling-4.0/flash-keyframe-to-video`。 Example：`kling-4.0/flash-keyframe-to-video`。
`callBackUrl`	`string`	No	The URL to receive generation task completion updates. Optional but recommended for production use. - System will POST task status and results to this URL when generation completes - Callback includes generated content URLs and task information - Your callback endpoint should accept POST requests with JSON payload containing results - Alternatively, use the Get Task Details endpoint to poll task status - To ensure callback security, see Webhook Verification Guide for signature verification implementation Example：`https://your-domain.com/api/callback`。
`input`	`object`	Yes	Input parameters for the generation task.
`input.prompt`	`string`	Yes	Video description. Required. Maximum 8000 characters. When `first_frame_url` is provided, mention it as `@first_frame`. Middle frames and a last frame are not supported on Kling 4.0 Flash — sending `keyframes` or `last_frame` is rejected. minLength: `1`. maxLength: `8000`. Example：`Animate the supplied image as one continuous 10-second shot. Keep the camera fixed to the opposite bench as the gondola ascends. Preserve the skier’s face, the goggles on her helmet, and the embroidered “ModelFold AI” patch.<br>REFERENCES: @first_frame is the exact opening frame.`。
`input.duration`	`integer`	No	Output video duration in seconds. Integer from 3 to 20. Default: `5`. Default：`5`。 minimum: `3`. maximum: `20`. Example：`5`。
`input.resolution`	`string`	No	Output resolution. Kling 4.0 Flash only supports `720p`. Default: `720p`. Default：`"720p"`。 Allowed values：`720p`。 Example：`720p`。
`input.aspect_ratio`	`string`	No	Output aspect ratio. `16:9`, `9:16`, `1:1`, or `21:9`. There is no `auto`. Only used when `first_frame_url` is omitted (text-to-video); default `16:9`. When a first frame is provided, the output follows that image's aspect ratio. Allowed values：`16:9` / `9:16` / `1:1` / `21:9`。 Example：`16:9`。
`input.first_frame_url`	`string`	No	Optional first-frame image URL. Mention it in the prompt as `@first_frame`. If omitted, the request is plain text-to-video. Middle frames (`keyframes`) and a last frame (`last_frame`) are not supported. pattern: `^https?://`.

Request Example

bash

curl -X POST "https://modelfold.ai/v1/jobs/createTask" \
  -H "Authorization: Bearer $MODELFOLD_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
  "model": "kling-4.0/flash-keyframe-to-video",
  "callBackUrl": "https://your-domain.com/api/callback",
  "input": {
    "prompt": "Animate the supplied image as one continuous 10-second shot. Keep the camera fixed to the opposite bench as the gondola ascends. Preserve the skier’s face, the goggles on her helmet, and the embroidered “ModelFold AI” patch.\nREFERENCES: @first_frame is the exact opening frame.",
    "first_frame_url": "https://static.aiquickdraw.com/tools/example/1793862976499_p1yBE2dY.png",
    "duration": 5,
    "resolution": "720p",
    "aspect_ratio": "16:9"
  }
}'

python

import os
import requests

resp = requests.post(
    "https://modelfold.ai/v1/jobs/createTask",
    headers={
        "Authorization": "Bearer " + os.environ["MODELFOLD_API_KEY"],
        "Content-Type": "application/json",
    },
    json={
        "model": "kling-4.0/flash-keyframe-to-video",
        "callBackUrl": "https://your-domain.com/api/callback",
        "input": {
            "prompt": "Animate the supplied image as one continuous 10-second shot. Keep the camera fixed to the opposite bench as the gondola ascends. Preserve the skier’s face, the goggles on her helmet, and the embroidered “ModelFold AI” patch.\nREFERENCES: @first_frame is the exact opening frame.",
            "first_frame_url": "https://static.aiquickdraw.com/tools/example/1793862976499_p1yBE2dY.png",
            "duration": 5,
            "resolution": "720p",
            "aspect_ratio": "16:9",
        },
    },
)
print(resp.json())

javascript

const resp = await fetch("https://modelfold.ai/v1/jobs/createTask", {
  method: "POST",
  headers: {
    "Authorization": "Bearer " + process.env.MODELFOLD_API_KEY,
    "Content-Type": "application/json",
  },
  body: JSON.stringify({
    "model": "kling-4.0/flash-keyframe-to-video",
    "callBackUrl": "https://your-domain.com/api/callback",
    "input": {
      "prompt": "Animate the supplied image as one continuous 10-second shot. Keep the camera fixed to the opposite bench as the gondola ascends. Preserve the skier’s face, the goggles on her helmet, and the embroidered “ModelFold AI” patch.\nREFERENCES: @first_frame is the exact opening frame.",
      "first_frame_url": "https://static.aiquickdraw.com/tools/example/1793862976499_p1yBE2dY.png",
      "duration": 5,
      "resolution": "720p",
      "aspect_ratio": "16:9"
    }
  }),
});
console.log(await resp.json());

package main

import (
	"fmt"
	"io"
	"net/http"
	"os"
	"strings"
)

func main() {
	body := strings.NewReader(`{"model":"kling-4.0/flash-keyframe-to-video","callBackUrl":"https://your-domain.com/api/callback","input":{"prompt":"Animate the supplied image as one continuous 10-second shot. Keep the camera fixed to the opposite bench as the gondola ascends. Preserve the skier’s face, the goggles on her helmet, and the embroidered “ModelFold AI” patch.\nREFERENCES: @first_frame is the exact opening frame.","first_frame_url":"https://static.aiquickdraw.com/tools/example/1793862976499_p1yBE2dY.png","duration":5,"resolution":"720p","aspect_ratio":"16:9"}}`)
	req, _ := http.NewRequest("POST", "https://modelfold.ai/v1/jobs/createTask", body)
	req.Header.Set("Authorization", "Bearer " + os.Getenv("MODELFOLD_API_KEY"))
	req.Header.Set("Content-Type", "application/json")
	resp, err := http.DefaultClient.Do(req)
	if err != nil {
		panic(err)
	}
	defer resp.Body.Close()
	out, _ := io.ReadAll(resp.Body)
	fmt.Println(string(out))
}

java

import java.net.URI;
import java.net.http.HttpClient;
import java.net.http.HttpRequest;
import java.net.http.HttpResponse;

public class Main {
    public static void main(String[] args) throws Exception {
        String body = "{\"model\":\"kling-4.0/flash-keyframe-to-video\",\"callBackUrl\":\"https://your-domain.com/api/callback\",\"input\":{\"prompt\":\"Animate the supplied image as one continuous 10-second shot. Keep the camera fixed to the opposite bench as the gondola ascends. Preserve the skier’s face, the goggles on her helmet, and the embroidered “ModelFold AI” patch.\\nREFERENCES: @first_frame is the exact opening frame.\",\"first_frame_url\":\"https://static.aiquickdraw.com/tools/example/1793862976499_p1yBE2dY.png\",\"duration\":5,\"resolution\":\"720p\",\"aspect_ratio\":\"16:9\"}}";
        HttpRequest req = HttpRequest.newBuilder()
            .uri(URI.create("https://modelfold.ai/v1/jobs/createTask"))
            .header("Authorization", "Bearer " + System.getenv("MODELFOLD_API_KEY"))
            .header("Content-Type", "application/json")
            .method("POST", HttpRequest.BodyPublishers.ofString(body))
            .build();
        HttpResponse<String> resp = HttpClient.newHttpClient().send(req, HttpResponse.BodyHandlers.ofString());
        System.out.println(resp.body());
    }
}

php

<?php
$ch = curl_init('https://modelfold.ai/v1/jobs/createTask');
curl_setopt_array($ch, [
    CURLOPT_CUSTOMREQUEST => "POST",
    CURLOPT_RETURNTRANSFER => true,
    CURLOPT_HTTPHEADER => [
        'Authorization: Bearer ' . getenv("MODELFOLD_API_KEY"),
        'Content-Type: application/json',
    ],
    CURLOPT_POSTFIELDS => '{"model":"kling-4.0/flash-keyframe-to-video","callBackUrl":"https://your-domain.com/api/callback","input":{"prompt":"Animate the supplied image as one continuous 10-second shot. Keep the camera fixed to the opposite bench as the gondola ascends. Preserve the skier’s face, the goggles on her helmet, and the embroidered “ModelFold AI” patch.\\nREFERENCES: @first_frame is the exact opening frame.","first_frame_url":"https://static.aiquickdraw.com/tools/example/1793862976499_p1yBE2dY.png","duration":5,"resolution":"720p","aspect_ratio":"16:9"}}',
]);
echo curl_exec($ch);
curl_close($ch);

csharp

using System;
using System.Net.Http;
using System.Text;

var client = new HttpClient();
var req = new HttpRequestMessage(new HttpMethod("POST"), "https://modelfold.ai/v1/jobs/createTask");
req.Headers.TryAddWithoutValidation("Authorization", "Bearer " + Environment.GetEnvironmentVariable("MODELFOLD_API_KEY"));
req.Content = new StringContent("{\"model\":\"kling-4.0/flash-keyframe-to-video\",\"callBackUrl\":\"https://your-domain.com/api/callback\",\"input\":{\"prompt\":\"Animate the supplied image as one continuous 10-second shot. Keep the camera fixed to the opposite bench as the gondola ascends. Preserve the skier’s face, the goggles on her helmet, and the embroidered “ModelFold AI” patch.\\nREFERENCES: @first_frame is the exact opening frame.\",\"first_frame_url\":\"https://static.aiquickdraw.com/tools/example/1793862976499_p1yBE2dY.png\",\"duration\":5,\"resolution\":\"720p\",\"aspect_ratio\":\"16:9\"}}", Encoding.UTF8, "application/json");
var resp = await client.SendAsync(req);
Console.WriteLine(await resp.Content.ReadAsStringAsync());

json

{
  "model": "kling-4.0/flash-keyframe-to-video",
  "callBackUrl": "https://your-domain.com/api/callback",
  "input": {
    "prompt": "Animate the supplied image as one continuous 10-second shot. Keep the camera fixed to the opposite bench as the gondola ascends. Preserve the skier’s face, the goggles on her helmet, and the embroidered “ModelFold AI” patch.\nREFERENCES: @first_frame is the exact opening frame.",
    "first_frame_url": "https://static.aiquickdraw.com/tools/example/1793862976499_p1yBE2dY.png",
    "duration": 5,
    "resolution": "720p",
    "aspect_ratio": "16:9"
  }
}

Response

200 — Request Successful

参数	类型	必填	说明
`code`	`integer`	否	See the response field; handle the returned status before retrying.
`msg`	`string`	否	Response message, error description when failed 示例：`success`。
`data`	`object`	是	—
`data.taskId`	`string`	是	Task ID, can be used with Get Task Details endpoint to query task status

json

{
  "code": 200,
  "msg": "success",
  "data": {
    "taskId": "task_kling-4.0-flash-keyframe-to-video_abc123"
  }
}

Callback

videoTaskCompleted

Callback URL: {request.body#/callBackUrl} (the callBackUrl in the request body).

The system POSTs this callback to callBackUrl when the kling-4.0/flash-keyframe-to-video task succeeds or fails.

Callback body parameters

参数	类型	必填	说明
`code`	`integer`	是	Unified callback code: `200` for success, `501` for failure. Allowed values：`200` / `501`。 Example：`200`。
`msg`	`string`	是	Unified callback message. Allowed values：`Playground task completed successfully.` / `Playground task failed.`。 Example：`Playground task completed successfully.`。
`data`	`object`	是	Task result. On success, `resultJson` contains `resultUrls`. On failure, `failCode` and `failMsg` are present and `resultJson` is omitted.
`data.completeTime`	`integer`	否	Task completion timestamp in milliseconds. Use this as the completion time.
`data.costTime`	`integer`	否	Processing time in seconds. Present on both success and failure callbacks.
`data.createTime`	`integer`	否	Task creation timestamp in milliseconds.
`data.model`	`string`	是	The model used for the task. Allowed values：`kling-4.0/flash-keyframe-to-video`。 Example：`kling-4.0/flash-keyframe-to-video`。
`data.param`	`string`	是	JSON string of the submitted task: `model`, `callBackUrl`, and `input`. `input` matches this endpoint's parameters (`prompt`, `duration`, `resolution`, `aspect_ratio`, `first_frame_url`).
`data.resultJson`	`string`	否	JSON string of the generation result. Present only when `state` is `success`. For this model it contains `resultUrls`, an array of `.mp4` URLs.
`data.state`	`string`	是	Terminal task state. Allowed values：`success` / `fail`。 Example：`success`。
`data.taskId`	`string`	是	The unique task identifier. Same as `data.taskId` returned by Create Task.
`data.updateTime`	`integer`	否	Task update timestamp in milliseconds. May equal `createTime`; use `completeTime` as the completion time.
`data.failCode`	`string`	否	Failure code, a numeric string such as `"400"` or `"500"`. Present only when `state` is `fail`.
`data.failMsg`	`string`	否	Failure reason. Present only when `state` is `fail`. For this model this may be a frame-count error (`duration 5s allows at most 6 frames (first + keyframes + last), got 7`), a missing `first_frame_url`, an undeclared `@first_frame` / `@keyframe_N` / `@last_frame` mention, or an upstream original message about image fetch/moderation/size.

Task completed successfully

json

{
  "code": 200,
  "data": {
    "completeTime": 1792670085074,
    "costTime": 718,
    "createTime": 1792669367000,
    "model": "kling-4.0/flash-keyframe-to-video",
    "param": "{\"input\":\"{\\\"duration\\\":10,\\\"keyframe_urls\\\":[],\\\"prompt\\\":\\\"女孩出门\\\",\\\"resolution\\\":\\\"720p\\\"}\",\"callBackUrl\":\"https://webhook.uutool.cn/bfa7de80-8dd8-4844-9e34-4032ddbbf3c1\",\"model\":\"kling-4.0/flash-keyframe-to-video\"}",
    "resultJson": "{\"resultUrls\":[\"https://tempfile.aiquickdraw.com/k/ce115adfa78260a99009eebddac1d187_1_1792670083_1582.mp4\"]}",
    "state": "success",
    "taskId": "ce115adfa78260a99009eebddac1d187",
    "updateTime": 1792669367000
  },
  "msg": "Playground task completed successfully."
}

Task failed

json

{
  "code": 501,
  "data": {
    "completeTime": 1792670085074,
    "costTime": 718,
    "createTime": 1792669367000,
    "failCode": "400",
    "failMsg": "duration 5s allows at most 6 frames (first + keyframes + last), got 7",
    "model": "kling-4.0/flash-keyframe-to-video",
    "param": "{\"input\":\"{\\\"duration\\\":5,\\\"first_frame_url\\\":\\\"https://example.com/first.png\\\",\\\"keyframe_urls\\\":[\\\"https://example.com/k1.png\\\",\\\"https://example.com/k2.png\\\",\\\"https://example.com/k3.png\\\",\\\"https://example.com/k4.png\\\",\\\"https://example.com/k5.png\\\"],\\\"last_frame_url\\\":\\\"https://example.com/last.png\\\",\\\"prompt\\\":\\\"女孩出门\\\",\\\"resolution\\\":\\\"720p\\\"}\",\"callBackUrl\":\"https://webhook.uutool.cn/bfa7de80-8dd8-4844-9e34-4032ddbbf3c1\",\"model\":\"kling-4.0/flash-keyframe-to-video\"}",
    "state": "fail",
    "taskId": "ce115adfa78260a99009eebddac1d187",
    "updateTime": 1792669367000
  },
  "msg": "Playground task failed."
}

Kling 4.0 Flash Keyframe To Video ​

Endpoint ​

Query Task Status ​

Related Resources ​

Request Parameters ​

Body (application/json) ​

Request Example ​

Response ​

200 — Request Successful ​

Callback ​

videoTaskCompleted ​

Kling 4.0 Flash Keyframe To Video

Endpoint

Query Task Status

Related Resources

Request Parameters

Body (application/json)

Request Example

Response

200 — Request Successful

Callback

videoTaskCompleted